Hunting is a condition in which a wheelset, truck or rail vehicle oscillates from side to side between rails of track while moving. Hunting may be caused by worn truck components, wear or defects in the track or rails or a variety of other reasons. Hunting results in rapid wear of truck and vehicle components, rails and other railway components, and has the potential to cause damage to cargo and perhaps eventually lead to derailment. The detection of hunting is important but relatively difficult. As such, a hunting condition may go undetected for a substantial period of time.
Angle of attack is generally defined as the yaw angle between wheels of a wheelset and rails. One measure of angle of attack is the angle between the plane of the wheel engaged on rail and a plane tangent to the rail. Angle of attack may also be shown by the angle between the axle centerline of a wheelset and a line that is either perpendicular to a rail or normal to the tangent of a rail. Angle of attack is a critical factor for assessing rail vehicle performance. For example, when the angle of attack is zero, the wheelset of a railway vehicle has equal magnitude and direction as the translational velocity of the railway vehicle resulting in greater efficiency of the railway vehicle. However, a positive angle of attack indicates a potential for a wheel set, truck or railway vehicle to climb the rails and even derail. Further, a positive angle of attack has the potential to generate transverse forces that may result in damage to railway and truck components and increase costs of maintenance and repair of such components.
Systems that detect hunting are currently available. For example, U.S. Pat. No. 5,622,338, the entirety of which is hereby expressly incorporated herein by reference, uses an acceleration sensor mounted to a truck for measuring acceleration of a rail car in a direction transverse to the rail. Such truck-mounted systems, however, are not suitable for use at a way station or a wayside, i.e., along the side or edge of a railroad track. Further, such truck-mounted systems are unsuitable for detecting hunting of individual wheels or wheelsets or measuring angle of attack of wheels, wheelsets, trucks or railway vehicles.
Systems are also currently available for measuring angle of attack. For example, angle of attack has been measured with a vehicle-mounted system associated with a particular wheelset as the rail vehicle travels on a track. Such vehicle-mounted systems are typically mounted to a particular wheelset, and therefore, are unsuitable for way station or wayside use or for determining angle of attack for all wheelsets on a railway vehicle. Further, because such systems are located on the vehicles themselves, the systems are less reliable and require more maintenance and supervision than a system suitable for way station or wayside use.
In addition, angle of attack has also been detected with a wayside mounted system. For example, U.S. Pat. No. 5,368,260, the entirety of which is hereby expressly incorporated by reference, uses a wayside rangefinder that incorporates a laser beam directed at a wheel to measure angle of attack between a plane of the wheel and a tangent of the track. The known wayside systems and methods for measuring angle of attack, however, are spaced substantially from the track and result in a static measurement which does not take into account dynamic misalignment of the rails due to train forces, environmental forces such as moisture and temperature changes, or misalignment of the wayside measuring systems due to the same or similar environmental forces. In addition, such systems are located to one side of the track making it unsuitable for directly detecting the angle of attack of wheels on the far rail. Further, laser beam systems are expensive, require continued maintenance and supervision and are prone to misalignment and malfunction due to the often treacherous railway environment and other moving objects associated with the environment.
Systems located adjacent to the rails of a railroad that measure angle of attack are also currently available. For example, U.S. Pat. No. 6,381,521, the entirety of which is hereby expressly incorporated by reference, discloses a method for determining angle of attack using vertical, lateral and angle of attack strain gages placed onto rails. Such systems, however, involve multiple types of gages to detect a number of forces and strain and require expensive and time consuming changes to track infrastructure or supplementation by other devices. For example, installation of strain gages on a rail typically requires grinding the rail and installing concrete rail sleepers. Further, as rail sections are changed out, the potential loss of strain gages makes strain gage technology impractical.
Further, known strain gage systems require precise location and installation of the gages, a time consuming and tedious process. For example, strain gages must be precisely located on a rail and often cannot be placed over a tieplate or sleeper as rail flexure needed to measure strain occurs between the sleepers. Moreover, the accuracy of strain gages may be compromised by temperature, material properties, the adhesive that bonds the gages to a rail, and the stability of the railway metal. For example, many strain gage materials are sensitive to changes in temperature and tend to drift and change resistance as they age. Further, calculating angle of attack based significantly on measurements of strain requires complex calculations.
Thus, there is a long felt need for an apparatus and method for both measuring angle of attack and detecting hunting of individual wheel sets as well as trucks and rail vehicles. In addition, there is a need for such an apparatus and method that is less susceptible to misalignment and poor signal quality due to external forces of the hazardous railway environment. Further, there is a need for such an apparatus and method that is inexpensive, easy to install, use and maintain, yet accurate in measuring angle of attack and detecting hunting.